Spark plug



R. J. BURTNETT July 14, 1936.

Patented July 14, 1936 UNITED STATES `PATENTA OFFICE 'I'he object of invention is to so construct 'thespark plug that the heat will befconducted to the engine body in a quick and eilicient manner to thereby not only prevent pre-ignition at the burning point, but alsoprotect the porcelain body against excessive heat and further to provide means whereby the sparking electrodes are more eilicient in action and more durable, as

Well as more readily replaceable when worn, as

more fully hereinafter set forth.'

In the drawing annexed: l

Fig. `l is a longitudinal sectional view of ay spark plug showing my preferred construction;

Fig. 2 is a bottom view of the plug, partly in horizontal section;

Fig. 3 is a horizontal section on the line,3-3 of Fig. 1;

Fig. 4 is a view partly in 4side elevation and partly in vertical section showing the forn of the plug without the expander disk; and

Fig. 5 is a detail view of the inner end of the central electrode. y

Referring to Figs. 1 and 2 of the drawing, by reference characters, I 0 designates the metal body of the plug which is constructed asusual, and II'is the usual porcelain rod, removably fastened in the tubular body `I0 in the usual manner and having the usual .rnetal electrode supporting rod I2 extending longitudinally through it. y

The extreme inner end ofthe conductor I2 has detachably attached to it a split ring I3 which forms the central electrode. This ring is adapted'to be snapped off and onto a headed pro- Jection I4 formed on the extreme inner end of the rod I2. Surrounding the annular electrode I3 is another annular, split ring electrode I5v shoulder I9 and also that before expanding the which is adapted to be snapped into end out of an annular groove formed in the interior of the plug body I0 at a. point coincident with the central electrode I3, the two electrodes being pro- .x portioned and separated so as to produce an annular/sp'ark gap between them. In practice, sparking may occur at any point around the facing circumferences of the electrodes, taking, of course, the easiest path.r From time to time, the point of sparking changes, with the result that in time sparking or arcing occurs entirely around the rims of the electrodes.- jlin-this Way, the electrodes will endure a great length of time as comparedwith the ordinary single sparking point device. vices renders fouling aremote contingency.

`The inner open end of the body III is closed by means of a disk I6 which convexes inwardly Also, this. arrangement of sparking deand is provided with aplurality of holes I1. Fuel mixture enters'the spark chamber only through these holes Il, and by proportioning these holes properly, the ignition pressure within the sparking chamber may be kept downl below that of the 5 ignition pressure in thecylinder, thereby reducing-the likelihood of fouling the spark electrodes 4 by the formation of carbon within the sparking chamber, and by the tendency to cause outwardly -moving jets through the holes I1 as the pressure lo on 'the Working stroke of the engine decreases. The main purpose, however, of the dome-'like disk I6 is to provide an efcient means for conducting the heat directly into the body II) and thence to the engine body; The edge of the disk 15 I 6 is held in hard metallic contact with the inner end of the body I0 and this insures quick distribution'of the heat intovthe tubular body I0.

For the purpose of detachably'attaching the dome-like disk I6 to the body I0, I form in the 20 interior of the body Il) at its extreme inner `end an under-cut annular groove, and I shape thev annular edge of the disk I6 so as to i'lt snugly therein, when the said annular .edge is expanded by means of an expanding disk I8 which is 9.5 clamped between the edge of the disk I 6 and a ,downwardly facing shoulder I 9 formed by the groove in the body I0.

It will be understood that the disk or ring I8 is of such size that when the cup I6 is forced 30 into the under-cut groove,.the annular edge of the ring I8 will cause the rim or edge of the cup to expand outwardly into the under-cut groove and thus lock not only the cup I6, but also the disk I8 solidly in place. It will be understood 35 that the disk I8 will be of such size as topa'ss, freely into the under-cut groove and against.

rim ofcup I6 said rim will pass freely into the groove, so that the parts may be readily assem- 40 bled. The disk I8 is provided with suitable openings to permit fuel to reach 'the sparking electrodes. The cup-like disk I6 is slightly flexible and expandibleto thus enable it to be solidly tted'into the under-cut groove; and to remove 45 the cup-like disk I6, it is necessary to merely use an appropriate tool; for instance, I may insert a punch down through the central bore of the plug and push it out of the under-cut groove.

It will be observed that the cup it attached di- `50 rectly to the ,barrel of the spark-plug proper and that thereforev the `heat will be dissipated to the engine body with a maximum of speed.

In Fig. 4, I omit the expander ring I8 and exn pand the edge of the cup by other means, as for 55 instance by beveling ,the shoulder I 9 outwardly and upwardly.

I propose using metals of different conductivity forI the cups I6; for instance, I may use copper for high pressure motors to getthe greatest heat conductivity possible; with standard motors, I may use -brass cups; and for' cold low-pres sure motors, I may use steel.A

I claim:

1. A spark plug embodying a, plug body whose inner end is grooved interiorly and a. cup-like perforated metal disk covering the open end of the plug body and enclosing the sparking; eie-1 disk being; expended to t into seid under-cut groove.

3. The structure recited in claim the metal.

disk being in the form of en irlwerrdiy-convexel ing cup and being expansible at its rim. portion,

and an open expander disk Whose anmnnr edge bears against the expensibe rim portion of the cup to lock the seme in the under-cut groove.

RIC J. BURTNE'IT. 

